CODEWITHSUNDEEP
javaarraysmultidimensional-arraycopy
Nyfiken Gul
Nyfiken Gul

Reputation: 684

Copy part of two-dimensional array

So I have a matrix M1 that I build at the beginning of my method each method call (this is all done in a non-static environment). The issue is that, depending on an integer index, say n I want the matrix M2 (in method call #2 for example) to contain rows 1, 2... n of M1 (the number of rows that I need for M changes each method call, but the number of columns persist).

My method in pseudocode;

int myMethod(numRows, numColumns, n) {

  Initialize M as matrix with dimensions(numRows, numColumns)
  if (n > 0) {
    **copy rows 1,2...,n from previous M matrix**
  }
  **do stuff with M**
  return M[numRows][numColumns];

What is a smart way to accomplish this? I hope it's clear what I'm asking for. Something worth noting is that Mi can be 'taller' or 'shorter' (it's always exactly as 'wide') as Mj for i > j

Upvotes: 0

Views: 1841

Answers (2)

manuel
manuel

Reputation: 36

Maybe return the array and pass the array as a parameter.

int[][] mymethod(int[][]oldArray, int noOfRows){
 int[][] newArr;
 if(noOfRows > 0){
  //here copy from oldArray to new;
  //sorry this is where I can't remember, you will have
  //to do something to get column size maybe oldArray[0].length()
  // but that may not work if each row has different length.
  newArr = new int[noOfRows][];
  for(int i=0; i < noOfRows; i++){
    for(int j = 0; j < noOfRows; j++){
     newArr[i][j] = oldArray[i][j];
    }
  }
 }
return newArr;
}

after this just call the method. int [][] a = mymethod(dArray,5); int [][] b = mymethod(a, 2);

Upvotes: 1

goliath16
goliath16

Reputation: 111

You could use a two dimensional vector, and then perhaps the clone() method. The awesome thing about vector is that it can grow and shrink as you need it to.

Upvotes: 1

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